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Equation Writing Review

Equation Writing Review. Complexes and PPT’s Acid-Base Redox Miscellaneous. AP Eq’n Writing Directions. Write the formulas to show the reactants and the products for the three laboratory situations described below. In all cases, a reaction occurs.

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Equation Writing Review

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  1. Equation Writing Review Complexes and PPT’s Acid-Base Redox Miscellaneous

  2. AP Eq’n Writing Directions • Write the formulas to show the reactants and the products for the three laboratory situations described below. • In all cases, a reaction occurs. • Assume that solutions are aqueous unless otherwise indicated. • Represent substances in solution as ions if the substances are extensively ionized. • Strong acids and ionic compounds are extensively ionized • Not dissolved means no ions!

  3. Directions (continued) • Omit formulas for any ions that are unchanged by the reaction. • Leave out spectators • Words like solid, liquid, gas, suspension, powdered, piece of, strip, etc… mean no spectators • One point penalty per reaction for showing spectators • You must balance the equation.

  4. Grading Equation Writing • 1 point for correct reactant formula(s) • 2 points for correct product formula(s) • 1 point for balancing • 1 point for answering simple related question • -1 for including spectators • There are often multiple acceptable product predictions

  5. Miscellaneous Equations - Organic • Organic • Combustion • Red flag is “burned” • Form oxides (CO2, H2O, …) • CS2 + O2 ---> CO2 + SO2 (or SO3) • Organic bases • Methylamine = CH3NH2 ---> CH3NH3+ = methylammonium • Ethylamine =C2H5NH2 • Dehydration synthesis: Can one lose H, the other OH? • Review basic organic families and their structures

  6. Misc. Equations - Synthesis • Putting two pieces together • The only possibility in reactions between two elements • P4 + O2 ---> P2O5 • Know strange allotropes? • P4, S8, diatomics • Criss-cross valences to get a reasonable product • Good option for non-aq rxns of elem + cmpd • NaS + O2 ---> NaSO3 (or similar) • Occasionally for non-aq rxn of two compounds • CaO + CO2 ---> CaCO3

  7. Misc. Equations - Decomposition • When a single compound is heated, you must break it up into smaller pieces • These can be a bit dicey • make common products: water, CO2 • avoid elements (requires redox) • Make 2 or 3 reasonable common products • Frequently gases • Carbonates ---> oxide + CO2 • Criss-cross to get formula of oxide • CaCO3 ---> CaO + CO2

  8. Review - Complex Eq’ns • Complex = Trans. Metal + Ligand • Common complexing agents (aka, ligands) • NH3, OH-, SCN-, CN- • Coordination number = # of ligands • Twice the valence of the Trans Metal • Be sure to carefully determine the correct charge on the complex

  9. Review - Precipitate Eq’ns • Common precipitating agents • Sulfide (S-2) • Hydroxide (OH-) • Carbonate (CO3-2) • Phosphate (PO4-3) • Silver, lead, mercury • Sulfate (SO4-2) with Ca, Ba, Sr • Know formulas and valences cold • Criss-cross valences to get correct formula of PPT

  10. Review - Acid Base Eq’ns • Look for obvious acid or base (don’t forget NH3) • Look at other reactant - is it a base or acid? • Proton transfer • Look for • Conjugates of weak acids • Fluoride, acetate, phosphate, • Conjugates of weak bases • Ammonium • Oxides, which are anhydrides • Metal oxides are bases, nonmetal oxides are acids • Carbonates, which do the fizzy reaction with acids

  11. Review - Redox Eq’ns • Memorize Redox “nuggets” • Permanganate, chromate, dichromate, nitric acid • Also, sulfuric acid, halogen/halide, metal/metal ion, two metal ions • Determine if the nugget is OX or RED • Determine if other reactant can be RED or OX • Add half-reactions and balance

  12. The Eq’n Writing Process • Scan the list of eight, and as you do • Cross out likely spectators • But ONLY if in solution • Sodium, potassium, nitrate are spectators • Sulfate can be a spectator, but look out for a PPT • Circle key words like solid, liquid, gas, suspension, powder, piece of …. • These indicate no spectators • Underline red flags • For Redox, AcidBase, PPT, Complex • Label rxn as AB, Comp, PPT, Redox, etc…

  13. Red Flags • Complex formation • Ammonia, hydroxide, thiocyanate, cyanide • Other reactant must contain a trans. Metal • PPT • Sulfide, hydroxide, carbonate, phosphate, Ag/Pb/Hg • Sulfate with barium/calcium • Acid Base • Acid, hydroxide, ammonia, oxide in water, carbonate • Redox • Permanganate, chromate, dichromate, nitric acid, peroxide

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